This invention relates to point-to-multipoint delivery of communication services and more particularly to broadcast systems operating in the millimeter frequency range.
Communication systems operating over a wide range of frequencies, modulation techniques, multiplexing techniques, error correction techniques, protocols, and network topologies are known in the state-of-the-art. Many recent papers have described numerous techniques for wireless transmission of two-way, switched narrowband services (e.g., TDMA time division multiple access) cellular, TDMA PCS (personal communication system), CDMA PCS (Code Division Multiple Access), etc. Many military systems such as JTIDS (Joint Tactical Information Distribution System), SINCGARS (Single Channel Ground and Airborne Radio System), PLRS (Position Locating and Report System), and MILSTAR (a military satellite communication system) have shown that wireless transmission can provide integrated voice and data services. It has been proposed that some form of television distribution or communication distribution systems may be provided by utilizing devices in the millimeter wave frequency band, which is between 28 GHz and 300 GHz using short range cellular transmitters covering small areas which are fed, e.g., by an underground cable in a manner similar to cellular radio. This distribution may also be made using microwaves converted at the local stations to the millimeter waves for local distribution. The distribution to millimeter wave stations may also be done by a fiber optic system or satellite distribution system.
A discussion of millimeter wave stations appears in the IEEE Spectrum of June 1982, pages 54-59, entitled, xe2x80x9cLow-Power Television-Short Range, Low Cost TV Stations are in the Offing as the FCC Prepares to Establish Broadcast Requirements.xe2x80x9d U.S. Pat. No. 4,747,160 entitled, xe2x80x9cLow Power Multi-function Cellular Television Systemxe2x80x9d of Bossard describes a low power, point to multipoint cellular television system operating in the 27.5 to 29.5 GHz frequency band with Omni-directional antennas. A 29 GHz point-to-point radio system for local distribution is described e.g., the British Telecom Technical Journal, vol. 2, no. 1, January 1984, entitled, xe2x80x9c29 GHz.-Point-to-Point Radio Systems for Local Distributionxe2x80x9d by S. A. Mohamed and M. Pilgrim.
It is highly desirable to provide some means to deliver improved broadband, wireless point-to-multipoint distribution service in millimeter frequency range.
In accordance with one preferred embodiment of the present invention, a low power, short range, wireless point-to-multipoint communication system is provided by a nodal transmitter located in a given node and a plurality of uni-directional transmitting antennas coupled to said transmitter are positioned to radiate in different directions from the node and about the node. The uni-directional antennas being of polarization types such that the polarization of the transmitted signal alternates about the node. A plurality of subscriber stations about the node have receiving antennas polarized to receive signals from a selected one of the uni-directional antennas.